The implementation of evidence-based practices (EBPs) is a priority for the Veterans Health Administration (VHA) and other healthcare systems. Supporting EBP implementation is seen as a crucial means by which to ensure that Veterans receive consistently high-quality and appropriate care. Cognitive- behavioral therapy for chronic pain (CBT-CP) is an EBP that is considered central to the interdisciplinary treatment of pain, and consequently VHA has invested substantial resources into system-wide training and certification for CBT-CP. Despite this substantial investment, practically nothing is known regarding the implementation of CBT-CP following initial training and certification, and based on implementation of other EBPs, there is good reason to believe that modification occurs frequently, with unknown impact on quality of Veterans' care. In order to prevent the waste of crucial VA resources and missed opportunities to improve Veterans' chronic pain treatment, an empirical understanding of what modifications are made to CBT-CP, why they are made, and the subsequent effects on implementation (including Veteran pain outcomes), is essential. Our project will include a VHA-Wide survey of CBT-CP providers that will assess common modifications made to CBT-CP in the field (Aim 1). This survey will also be used to identify participants in a prospective observational study of provider motivations to modify CBT-CP (Aim 2) as well as the effects of modification on Veteran outcomes (Aim 3a) and CBT-CP implementation (Aim 3b). Aim 1 will be achieved through a national survey. These data will also be used to target recruitment for Aims 2 and 3. A stratified random sampling of Aim 1 respondents and Veterans receiving their care will be selected for a prospective naturalistic observational study of CBT-CP modifications and their effects. Clinicians will complete semi-structured interviews regarding modification at baseline and follow-up. We will examine the association between change in Veteran outcomes and type and extent of modifications. Implementation will be assessed through the lens of Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM). RE-AIM variables will be assessed via a combination of record review/administrative data, Veteran interviews, and clinician self-report. Analyses of Aim 1 will be descriptive in nature. In order to test the relationship between provider motivation and modification in Aim 2, we will use Pearson's correlations, and interview responses regarding reasons for modification will be analyzed using inductive analyses. Multi-level mixed effects models will be used to examine the relationship between modification and change in Veteran outcomes (Aim 3). Results will provide vital information regarding the impact of current CBT-CP implementation efforts, factors which may affect provider behavior, and help maximize productive modifications associated with positive Veteran outcomes.